The present invention is related to an electric brake device which performs braking operation by pressing a brake pad against a rotation face of a brake rotor in a direction perpendicular thereto with an electric actuator.
Recently, in a disc brake device which is used in a vehicle, with an increase of electric cars using an electric motor as a motive power, it is impossible to employ a braking force servo device which utilizes negative pressure generated by a motive power using fuel such as gasoline. Therefore, in order to install the conventional hydraulic brake system in the electric car or the like, a servo unit such as a vacuum pump is necessary. However, in this case, brake pipes and a hydraulic control unit may increase a weight of the vehicle. In view of the above, for the purpose of reducing the weight of the vehicle and abolishing the hydraulic system, and because a regenerative brake is easily controllable, an electric brake device has been proposed. An electric disc brake is intended to press a friction member such as a brake pad against a brake rotor which is rotating, by converting a rotation torque by the electric actuator to a normal force by means of a reducer and a linear conversion device.
Further, an electric servo-disc brake which performs braking operation by a mechanical self-servomechanism utilizing a wedge action or so is employed thereby to attain higher efficiency. By employing such electric servo-disc brake, it is possible to reduce a size of the electric actuator and consumption of power, and also, contribution to an increase of a running distance of the electric vehicle such as the electric car and downsizing of a battery can be expected. In the electric brake device as described above, friction coefficient of the friction material of the friction brake is constantly fluctuated. However, to cope with such fluctuation, actual relation between a power supply value to the motor, which is the electric actuator, and a braking torque value of the brake is not gained to be utilized, and accurate control has not been performed. Under the circumstances, the electric brake which performs braking control with high accuracy as disclosed in the following Patent Document 1 has been proposed.    [Patent Document 1] Japanese Patent Publication Number 11-043041